An undated still image of a video footage released on Thursday, shows a portrait of Kenneth Bae. Mr. Bae, the Korean-American arrested in November 2012 and accused of attempting to overthrow the government, is a devout Christian.

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Washington — North Korea’s sentencing on Thursday of a US citizen to 15 years of hard labor could be a ploy by leader Kim Jong-un to get a high-profile American visit and burnish his leadership standing.

But there may be another explanation for what is the toughest sentence ever handed to an American by a North Korean court, some North Asia analysts say. Kenneth Bae, the Korean-American arrested in November 2012 and accused of attempting to overthrow the government, is a devout Christian.

Mr. Bae, a tour operator from Washington state who was living in a Chinese city near North Korea, was charged with carrying out “hostile acts” against the state that included having unspecified materials in his possession that prompted the accusations of planning the overthrow.

Was Bae carrying a Bible when he was arrested? The North Korean regime is particularly harsh with anyone found with a Bible, says Mr. Green, now the senior vice president for Asia at the Center for Strategic and International Studies in Washington.

Friends of Bae have speculated that he may have taken pictures of starving North Korean children or even of executions – neither of which would please North Korean authorities. Bae reportedly was living in the Chinese city of Dalian and frequently crossed the border to take food to orphans, according to friends. But the scant information released by the North Korean government left unclear exactly what Bae had done.

“Kenneth Bae had no access to a lawyer. It is not even known what he was charged with,” Amnesty International said in a statement Thursday.

The State Department, meanwhile, called for Bae's "immediate release." In a statement, spokesman Patrick Ventrell said the US had "longstanding concerns" about the lack of transparency and due process in the North's judicial system. But he added that "now that [Bae] has gone through a legal process we urge the DPRK [the Democratic Peoples Republic of Korea] to grant him amnesty and immediate release."

Bae’s sentencing prompted speculation that Mr. Kim, the North’s young new ruler, could be angling for a news-grabbing visit from an American dignitary to try to win clemency. Bae is at least the sixth American to be found guilty of some unspecified crime against the North Korean state. Earlier cases have led to visits from two former presidents – Jimmy Carter and Bill Clinton – and from Bill Richardson, the former US ambassador to the UN.

President Clinton won the release of two American women journalists, Laura Ling and Euna Lee, in 2009 while his wife, Hillary Rodham Clinton, was secretary of state. President Carter undertook a similarly successful mission in 2010 on behalf of Aijalon Mahli Gomes, an American who, like Bae, was said to be a devout Christian.

After a flurry or reports out of South Korea that Carter was about to undertake a trip to Pyongyang on Bae’s behalf, the former president’s press secretary told Reuters that Carter “has not had an invitation to visit North Korea and has no plans to visit.”

Earlier this week the State Department had issued a statement calling on North Korea to release Bae “on humanitarian grounds.”

Already-tense US-North Korea relations have deteriorated further in recent months after Pyongyang conducted a third nuclear test in February and the US carried out annual joint exercises with the South Korean military. Kim managed to place himself on US and international front pages by threatening to “incinerate” US cities.

The heated rhetoric has cooled, although tensions could flare anew if the North conducts a ballistic missile test soon, as some experts anticipate.

But Bae’s sentencing may represent a renewed effort to put the North and Kim in the international spotlight at what for Kim maybe a critical moment, some regional experts say.

Their reasoning? South Korea’s new president, Park Geun-hye, will visit the US next week on a multicity tour that will feature a White House dinner and a speech to a joint session of Congress. President Park will be dominating headlines that Kim may feel should be his.